1. Field of the Invention
This invention relates to a socket for use with integrated circuit components and more particularly to a burn-in socket for use in testing gullwing leaded integrated circuit components.
2. Description of the Prior Art
In order to insure the reliability of integrated circuit components, it has long been necessary to subject these components to accelerated heat-age testing. This so called burn-in testing is sometimes conducted for all components and in other cases is conducted on a statistical basis to insure that the components in questions will perform satisfactorily.
Burn-in sockets have been employed to test integrated circuit devices such as IC chips. A plurality of burn-in sockets can be disposed on a printed circuit board which is then positioned within a burn-in oven to subject the integrated circuit chips or chip packages to heat-age testing. Burn in sockets have been developed for use with leadless ceramic chip carriers, with through hole leaded dual-in-line packages (DIP's) and for leaded surface mount components.
One such burn-in socket for use in testing leadless chip carriers, is disclosed in U.S. Pat. No. 4,491,377. That socket includes an insulating base support containing a plurality of electrically conductive pins extending through the insulating base. A spreader is mounted for reciprocal movement relative to the pins. The spreader has an inclined surface engaging edges of the pins so that movement of the spreader toward the insulating base shifts the pins outwardly. A leadless chip carrier can then be inserted into a cavity surrounded by the pins. The pins can thus make contact with terminal lands within grooves on the edge of the leadless chip carriers.
The zero insertion force socket disclosed in U.S. Pat. No. 4,491,377 provides certain advantages when used with automatic loading equipment. Actuation of the spreader in that socket can be accomplished by straight line motion in the same direction in which a leadless chip carrier would be loaded into the socket. Individual chip carriers can be positioned in an insertion head. The insertion head would be brought into contact with the spreader on the socket, which would shift the terminal pins to allow room for insertion of a chip carrier, held on the insertion head. Extraction of a leadless chip carrier could be accomplished in the same way. When the socket shown in U.S. Pat. No. 4,491,377 is employed with plastic leadless chip carriers or leadless chip carriers, these chip carriers must be located upside-down or in the "dead bug" configuration.
The advent of new integrated circuit packages has however, lead to additional complications for burn-in testing and for sockets used for burn-in testing. The plastic quad flat pack package (PQFP) has gullwing leads located on four sides of a rectangular or square plastic body. Standard versions of these low profile plastic quad flat packages have gullwing leads on 0.025 inch center line spacings. These gullwing leads extend from all four sides of the body of the PQFP device. The lower portions of the gullwing leads have outwardly extending feet which extend below the lower surface of the body of the PQFP. Typically, these feet are slightly inclined relative to the horizontal, for example, from 0 degrees to 8 degrees. In use, a PQFP could be soldered to surface mount pads on a printed circuit board. These leads are generally plated in a conventional manner to promote a reliable solder joint. It is important that the lower surface of these plated leads not be damaged during burn-in testing. These gullwing leads are relatively small and fragile and care must be taken not to overstress or damage the leads during burn-in testing. Sockets of the type shown in U.S. Pat. No. 4,491,377 are not suitable for use with PQFP or quad pack components. It is possible to separately attach an adaptor to the plastic quad flat packages so that the adaptor supports the leads. The PQFP packages mounted in an adaptor of that type can then be inserted into a socket such as that shown in U.S. Pat. No. 4,491,377.
However, the efficiencies otherwise obtained by using a socket of the type shown in U.S. Pat. No. 4,491,377 in conjunction with automatic loading equipment would be reduced or eliminated if it is necessary to first mount the plastic quad flat packages in an adaptor. The present invention, however, comprises a socket suitable for use with gullwing packages, such as PQFP's, without requiring an additional adaptor.